1. Field of the invention.
The present invention relates to a barge used for temporary storage of oil. Such barges are used where oilfields are being developed or tested in marine environments.
2. Description of the Related Art
Where an oilfield is under development, a considerable volume of oil may be produced at the site of a new well before it becomes possible to export oil from the well-site by means of a pipeline or shuttle tanker. In particular, testing to determine the quality of oil being produced may be required before it is decided to proceed with a permanent or pseudo-permanent connection to pipelines.
It has been difficult, hitherto, to provide suitable temporary oil storage facilities during the initial phase of development of an oil field. It is difficult to moor or position an existing vessel or tanker close to a drilling platform if the platform is in deep water or in a harsh environment. Existing schemes have used dynamically positioned tankers or tankers with special mooring systems in shallower water (up to 120 meters) or have used modified supply boat hulls as containers to store oil on a temporary basis. This latter option, in particular, is expensive. The capital cost involved in acquiring and using such vessels is high and, since testing of oil wells is carried out on a seasonal basis, the vessels are under-utilised for at least a part of the year.
There is therefore a need for a low cost, convenient storage facility which offers temporary storage at the locations at which well testing, logging, or cleaning take place. Ideally, such storage facilities should be such that they can easily be moored in water depths from shallow (a10-15 meters) up to at least the present limit of drilling operations, say more than one thousand meters.
It is also desirable from an economic point of view that any vessel used as a temporary storage means should be classified under international regulations as an unmanned barge. In order to achieve this installations for use in ballasting, de-ballasting or oil-pumping should be carried by attendant vessels and not carried by the storage vessel itself except, perhaps, temporarily when needed. This has the additional advantage that areas which would normally be taken up by such installations are kept free.
In accordance with the invention there is provided an oil storage vessel, the vessel comprising a hull at least partially enclosing a storage chamber for containing oil and provided with a plurality of ballast chambers, the orientation of the hull relative to water in which it is floated being controllable by adjusting the content of some or all of the ballast chambers ; said hull being adapted for displacement in a horizontal orientation while the storage chamber is full, whereby said vessel is suitable for the transport of oil.
Preferably the hull is generally cylindrical in shape and is formed at least in part of a wall comprising inner and outer skins; the ballast chambers being formed in the wall of the hull between inner and outer skins thereof.
The vessel may be provided with inlet valve means for controlling the flow of material into the storage chamber and/or ballast control means for adjusting the content of the ballast chambers; the inlet valve means and/or the ballast control means being provided with means for connection to an umbilical line permit control from a remote location, for example, an attendant support vessel.
The invention can thus provide relatively inexpensive, easily maneuverable means for the temporary storage of oil which is, additionally, suitable for classification as an unmanned barge.